Filling machines for filling packaging containers made of cardboard composite material with products, in particular liquid foods, are known from the prior art. For example, reference is made to EP 0 936 992 B1 and DE 41 42 167 C2 for the construction of known filling machines.
The conventionally cuboid packaging containers are only made once they are in the filling machine, from packaging blanks which are provided with fold edges and welded together to form packaging jackets, because this improves transportability. Each packaging jacket that is folded flat has four packaging walls, which are separated from one another by parallel outer and inner fold edges. An acute internal angle is formed in each case between the packaging walls at the outer fold edges of the packaging jacket when it is folded flat. The inner fold edges of the folded-flat packaging jacket are arranged between the outer fold edges. An obtuse internal angle is formed in each case between the packaging walls at the inner fold edges of the packaging jacket when it is folded flat. If the packaging walls have mutually similar dimensions, the inner fold edges divide in half the length between the outer fold edges.
The folded-flat packaging jackets are supplied from a magazine to the at least one conveying line of the filling machine. In the magazine, the packaging jackets are arranged as a stack, conventionally standing upright, one behind the other. On a removal side of the magazine which points in the direction of the conveying line, two of the four packaging walls of the packaging jacket which is respectively at the front are exposed. A force, for example from a spring or a linear drive, acts on the stack at its rear side and in the direction of the removal side, in order to shift the packaging jackets of the stack toward the removal side.
A removal and unfolding device includes a gripper for taking hold of one of the two packaging walls that is exposed at the removal side of the magazine, a guide for the other of the two exposed packaging walls, and holding elements, arranged behind the guide as seen in the direction of motion, for receiving the outer fold edges of the unfolded packaging jacket.
The removal and unfolding device unfolds the initially folded-flat packaging jacket to form a packaging jacket which, as seen in cross section, forms a rectangle. The unfolded packaging jacket is transferred to a transport means. As they pass along the conveying line of the filling machine, the packaging containers which are made from the packaging jackets are sterilized, filled and then sealed. Conventionally, the packaging base is made directly before filling. Then, conventionally the packaging top is made.
As the transport means there are used in particular transport wheels or circulating conveyor belts having pocket-shaped receivers for the unfolded packaging jackets or packaging containers. The transport wheels, which rotate stepwise, have a plurality of radially outwardly extending parallel receivers. The receivers conventionally take the form of mandrels onto which the unfolded packaging jackets or packaging containers are pushed; this unit is then called a mandrel wheel. In another construction of a transport wheel of this kind, each receiver includes a plurality of arms or profiles which abut against the outside of the unfolded packaging jacket or packaging container, in particular directly next to the fold edges. In this case the receivers form cells into which the unfolded packaging jackets or packaging containers may be pushed; this unit is then also called a cell wheel.
A filling machine that is part of the prior art and has a removal and unfolding device, from SIG Combibloc GmbH in 52441 Linnich in Germany, will be explained in more detail below with reference to FIGS. 1 a-1 d: 
The packing jackets (1), which are folded flat, are stored in the magazine (2) of the filling machine. Each folded-flat packaging jacket (1) has four packaging walls (5a, 5b, 6a, 6b) which are separated from one another by parallel outer fold edges (3a, 3b) and inner fold edges (4a, 4b).
The two forwardly pointing packaging walls (5a, 5b) of the respectively front packaging jacket (1) are exposed at a removal side (7) of the magazine (2). So that the packaging jackets (1) do not fall out of the magazine at the removal side (7), retaining elements (8a, 8b) are arranged at the removal side (7) and extend along the outer fold edges (3a, 3b) of the front packaging jacket (1). The respectively front packaging jacket (1) is not removed across the full width of the two packaging walls (5a, 5b). Rather, the packaging jacket (1) is only taken hold of at one of the two exposed packaging walls (5a) of the packaging jacket (1), at the removal side (7) of the magazine (2) (cf. FIG. 1 a). A suction gripper (9) which is secured to a pivotal arm (11) arranged to pivot about an axis (10) serves to take hold of the packaging wall (5a). As a result of a pivotal movement of the suction gripper (9) about the perpendicular axis (10), first the outer fold edge (3a) is freed from the retaining element (8a), wherein as the pivotal movement of the suction gripper (9) continues about the opposite outer fold edge (3b), which is still held by the retaining element (8b), a flat parallelogram is formed, as can be seen in particular from FIG. 1a. In the course of the further pivotal movement, first the outer fold edge (3b) is freed from the retaining element (8b). Then, the packaging jacket (1) is guided by means of the other of the two exposed packaging walls (5b) sliding along a curved guide surface (12) of a guide element (13). As the packaging jacket (1) moves along the path of motion (14), the guide surface (12) has the effect of making the acute internal angles (15a, 15b) larger, wherein the internal angle (15a) is formed between the packaging walls (5b, 6b) and the internal angle (15b) is formed between the packaging walls (5a, 6a). As seen in the direction of the path of motion (14), at the end of the curved guide surface (12) there is a holding element (16) which takes the form of a groove-shaped depression made in the guide element (13). The holding element (16) serves to receive the outer fold edge (3b) of the unfolded packaging jacket (1). Also as seen in the direction of the path of motion (14), downstream of the guide surface (12) there is a further stationary holding element (17) in the form of a holding strip (17) for receiving the diametrically opposed outer fold edge (3a). The holding elements (16, 17) are spaced and aligned such that the packaging jacket received by the holding elements (16, 17) forms a rectangle as seen in cross section. This alignment is required for unproblematic transfer of the unfolded packaging jacket to the transport means downstream of the removal and unfolding device, such as in particular the transport wheels mentioned at the outset. At the end of the curved guide surface (12), the initially acute internal angle (15a, 15b) of the packaging jacket briefly becomes slightly greater than 90°, as can be seen from FIG. 1c, in order to ensure that the fold edge (3b) latches unproblematicaliy into place in the holding element (16).
The fold edges (3a, 3b, 4a, 4b), in particular the inner fold edges (4a, 4b) of the packaging jacket (1), create restoring moments which act in opposition to unfolding of the packaging jacket (1). As the packaging jacket (1), which is initially folded flat, unfolds to form a packaging jacket which is rectangular as seen in cross section, the restoring moments increase. As can be seen in particular from FIG. 1b, the line of contact between the packaging wall (5b), which is guided in sliding manner, and the guide surface (12) extends approximately in the centre of the packaging wall, parallel to the fold edges (3b, 4a) that delimit the packaging wall (5b). Because the restoring moments increase as unfolding continues along the path of motion (14), increasing contact pressure forces between the packaging wall (5b) and the guide surface (12) are also produced. The powerful contact pressure force, increasing along the path of motion, requires a powerful suction force from the suction gripper (9) in order to hold the packaging jacket (1) securely during the removal and unfolding movement. Because a high throughput rate is required of filling machines during filling of the packaging containers, removal and unfolding of the packaging jackets must be carried out at a correspondingly high speed. This has the result that the packaging jackets (1) are drawn along the guide surface (12) and into the holding elements (16, 17) at high speed, which because of the unavoidable latching of the packaging jacket into place in the holding element (16) results in the development of considerable noise. Finally, relatively powerful transverse forces, both during latching of the packaging jacket into place in the holding element (16) and during the unfolding movement along the guide surface (12), are produced between the suction elements of the suction gripper (9) and the packaging wall (5a). If the holding forces of the suction gripper are exceeded during this, the packaging jacket that is taken hold of may be unintentionally released and hence operation of the entire filling machine may be disrupted. Moreover, the powerful contact pressure forces between the guided packaging wall and the guide may cause abrasion marks on the packaging wall.
EP 0 766 621 B1 discloses a device for removing a packaging jacket from a magazine and for unfolding the packaging jacket to give a rectangular cross section, wherein a gripper that is arranged to pivot about an axis of rotation takes hold of one of the two exposed packaging walls of the folded-flat packaging jacket at the removal side of the magazine. Moreover, the device has a guide that is arranged to pivot about an axis and takes the form of a flap which is pivotal by means of a drive from a first position into a second position. Further, the device has a stationary holding element for receiving one of the two outer fold edges of the packaging jacket, which has not yet been completely unfolded. However, the opposite fold edge is not taken hold of by a holding element. Rather, the packaging wall that is not taken hold of by the gripper abuts flush against the pivotal flap.
Pivoting the flap clockwise about the axis has the effect of completely erecting the packaging jacket, with the result that the cross section of the packaging jacket is rectangular. During this, the packaging wall that abuts against the pivotal flap slides along the flap until, in the end position of the pivotal flap, a lug that is arranged on the end of the flap receives the second outer fold edge. The suction gripper can only be released once the packaging jacket has been completely erected to give a rectangular cross section, since otherwise the restoring forces of the packaging jacket would cause it to slide out of the device. A further disadvantage of the device consists in the fact that, in the phase when the restoring forces are greatest, that is to say when the packaging jacket is completely erected, the packaging jacket abuts flush against the flap and performs a motion in relation thereto, as a result of which a relatively high level of wear and damage to the packaging wall may result.